#include <opencv2/opencv.hpp>

int main(int argc, char** argv){
    cv::Mat img_rgb, img_gry, img_cny, img_pyr, img_pyr2;

    cv::namedWindow("Example Gray", cv::WINDOW_AUTOSIZE);
    cv::namedWindow("Example Canny", cv::WINDOW_AUTOSIZE);

    img_rgb = cv::imread(argv[1]);

    cv::cvtColor(img_rgb, img_gry, cv::COLOR_BGR2GRAY);
    cv::pyrDown(img_gry, img_pyr);
    cv::pyrDown(img_gry, img_pyr2);
    cv::Canny(img_pyr2, img_cny, 10, 100, 3, true);
    cv::imshow("Example Canny", img_cny);

    cv::waitKey(0);
    cv::destroyWindow("Example Gray");
    cv::destroyWindow("Example Canny");
}